It's a comfortable mattress however I'd say it is "soft-medium" rather than "medium-firm". 

I had to sleep on the mattress on the floor for a couple of days and I found it very comfortable however after we moved it to the bed frame with wooden slats I have found it a little softer than I would like and I am confused by the other reviews saying it is too firm. 

I am used to sleeping on a memory foam only mattress which felt firmer. If I was to buy again I would go for one of Dormeo's memory foam only mattresses (which have a much longer warranty too).